[jira] [Created] (CASSANDRA-6483) Possible Collections.sort assertion failure in STCS.filterColdSSTables

["graham sanderson (JIRA)" <ji...@apache.org>]

graham sanderson created CASSANDRA-6483:
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             Summary: Possible Collections.sort assertion failure in STCS.filterColdSSTables
                 Key: CASSANDRA-6483
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6483
             Project: Cassandra
          Issue Type: Bug
          Components: Core
            Reporter: graham sanderson


We have observed the following stack trace periodically:

{code}
java.lang.IllegalArgumentException: Comparison method violates its general contract!
        at java.util.TimSort.mergeLo(TimSort.java:747)
        at java.util.TimSort.mergeAt(TimSort.java:483)
        at java.util.TimSort.mergeCollapse(TimSort.java:410)
        at java.util.TimSort.sort(TimSort.java:214)
        at java.util.TimSort.sort(TimSort.java:173)
        at java.util.Arrays.sort(Arrays.java:659)
        at java.util.Collections.sort(Collections.java:217)
        at org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy.filterColdSSTables(SizeTieredCompactionStrategy.java:94)
        at org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy.getNextBackgroundSSTables(SizeTieredCompactionStrategy.java:59)
        at org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy.getNextBackgroundTask(SizeTieredCompactionStrategy.java:229)
        at org.apache.cassandra.db.compaction.CompactionManager$BackgroundCompactionTask.run(CompactionManager.java:191)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
        at java.util.concurrent.FutureTask.run(FutureTask.java:262)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:744)
{code}

The comparator ant SizeTieredCompactionStrategy line 94 breaks the assertions in the new JDK7 default sort algorithm, because (I think just) the hotness value (based on meter) may be modified concurrently by another thread

This bug appears to have been introduced in CASSANDRA-6109




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